DESCRIPTION: (Applicant's Description) The purpose of the NOD/SCID mouse core is to: (a) provide projects 1, 2, 3, and 5 with healthy, quality controlled NOD/SCID mice for experimentation, (b) assist with transplant conditioning regimen and transplantation procedures, (c) advise on the setup and evaluation of transplant experiments, and (d) examine the attributes of alternative and possibly superior mouse models for transplantation of human hematopoietic cells which are currently available or which may become available during the proposed granting period.